Method and apparatus for transmitting and receiving audio over analog video transmission over a single coaxial cable

ABSTRACT

Disclosure herein includes descriptions of a method for transmission of digital audio over analog video data with a single cable. The method comprising receiving, by a video transmitter, a digital video signal and one of a digital or an analog audio signal. Sampling, by an audio analog-to-digital converter (ADC), the audio signal if it is an analog audio signal. Storing, in a First-in-First-Out (FIFO) buffer, digital audio data corresponding to the sampled analog audio signal; reading, by an arbiter, the digitized audio samples, in response detecting an availability of data in the FIFO buffer and formatting the serialized audio bits with a digital start code; inserting the serialized audio bits and the digital start code into a blanking period of the digital video signal, thereby generating a combined digital audio and video signal and converting, by a digital-to-analog converter (DAC), the combined digital audio and video signal to analog, thereby generating a combined analog audio and video stream including audio data in a native form; and transmitting the combined analog audio and video stream to a receiver in one direction. In another embodiment, an analog signal is transmitted in the opposite direction.

FIELD

The application relates in general to digital video transmission and inparticular to methods and apparatuses for transmitting and receivingaudio over analog video transmission over a single coaxial cable.

BACKGROUND

It is apparent when it comes to the need to send both analog audio andvideo data over a distance; one cable is better than two cables in termsof cost and complexity. Various methods and apparatuses have beenproposed to reduce the cost and complexity of sending both analog andvideo signal by transmission over a single coaxial cable. To avoidinterference between the analog audio and video data on a single cable,there are potentially two ways to get the required separation. Frequencymultiplexing audio data and video data and transmitting each data signalover distinct non-overlapping frequency band is known. Interleaving anaudio signal and a video signal in the time domain thereby having theaudio and video data present in the signal at different times withoutinterfering with each other is known. Interleaving audio data whenactive video is not present during the video-blanking is also known.However, current signaling protocols are complex and require intensivecalculation for interleaving audio data in with video data.

For example, U.S. application Ser. No. 14/442,803 of Zhejiang DahuaTechnology Co., Ltd. discloses a method of and apparatus fortransmitting a high-definition video signal to address the problem inthe prior art, i.e., the cost and complexity of transmitting analog andaudio over a distance using a single coaxial cable. In particular, the'803 Application proposed to buffer audio data by calculating an audioduration for every each row in the video frame that audio data issuperimposed. However, the proposed method of the '803 Applicationcreates the need to for calculating and storing an audio duration sizein every active row of video data. Doing so requires storing andbuffering audio durations that are not small and require burdensomebuffering and storage requirements, which complicates the coding scheme.The exemplary implementations described herein do not requirecalculating the number of audio samples to be stored in the buffer andtransmitted per frame basis and employs much smaller buffer, reducingcost of manufacture and operating power requirements.

Accordingly, there remains a need in the art for a solution thataddresses the problems discussed above among others.

SUMMARY

One or more embodiments herein relate generally to a method and systemfor transmitting digital audio and video data over a transmission mediumin analog form using a single coaxial cable. More specifically, one ormore embodiments herein disclose a method or apparatus for efficientlytransmitting audio data in a video blanking period of an analog videosignal in a manner that does not require intensive calculation of theaudio duration on a row by row basis.

According to one aspect, a method of one or more embodiments herein mayinclude receiving an audio signal in analog or digital form, andquantizing the signal if in the analog form into a digital format toresult in a plurality of quantized audio data. The method includesbuffering one or more of the plurality of quantized audio data andreceiving a video signal that includes a blank interval and at least oneportion of video data disposed therein. In some embodiments, the methodincludes generating one or more quantized audio pulses corresponding tothe one or more of the plurality of quantized audio data stored in thebuffer and an audio header corresponding to the one or more quantizedaudio pulses. The method includes identifying, without calculating, atleast one permissible portion of the blank interval corresponding to afirst duration exceeding a predetermined duration of the audio headerand the one or more quantized audio pulses. The method may conclude, insome embodiments, by multiplexing, in the at least one permissibleportion of the blank interval, the audio header and the one or moreaudio pulses, with the at least one portion of video data resulting in acombined audio and video signal that represents at least a portion ofthe audio and video data.

According to another aspect of the invention a method of one or moreembodiments herein may include receiving an analog video signal, theanalog video signal including an audio header and one or more quantizedaudio pulses corresponding to quantized audio data, and detecting theaudio header in a blank interval of the analog video. In someembodiments, the method includes, determining a reference level of theaudio header, and extracting, in response to detecting the audio header,the one or more quantized audio pulses. In some embodiments, the methodincludes converting the one or more quantized audio pulses to anoriginal value of the one or more quantized audio data based on thereference level of the audio header and storing the one or morequantized audio data in the original value in a First-in-First-Out(FIFO) buffer. In some embodiments, the method includes reconstructing,utilizing the FIFO buffer, continuous audio data from the one or morequantized audio data in the original value. For example, audio sampledata stored in the FIFO buffer and a local audio clock that hassubstantially the same frequency as the original sampling clock at thetransmitter side. Substantially the same means the difference isnegligible.

Another aspect of one or more embodiments may include a method andapparatus for transmitting digital audio over analog video data with asingle cable. The method includes receiving, at a transmitter, a digitalvideo signal and an audio signal in analog or digital form, andsampling, by an analog-to-digital converter (ADC), the analog audiosignal, if in analog form. The method includes storing, in aFirst-in-First-Out (FIFO) buffer, audio bits corresponding to thedigital audio signal or sampled analog audio signal and reading, by anarbiter, the audio bits that have been serialized for output, inresponse detecting an availability of data in the FIFO buffer. Thearbiter can detect the availability of the video blanking period andaudio sample data in the FIFO before releasing one data sample from FIFOby serializing the sample data and at the same time appending a digitalheader or start code in the beginning of the sequence. Each FIFO entrycontains one audio sample data converted by the ADC. The number of bitsper sample depends on the ADC resolution. Serialization of bits fordigital transmission happens at the output. These bits are representedby a digital value with certain duration and they will be subsequentlyconverted to a pulse with certain height and duration by the DAC. Theanalog audio transmission works in a similar fashion except that theoutput of the arbiter are digital codes representing the start pulseheight followed by audio sample code(s) all with some time duration sothey will be analog pulses after converted to analog format by DAC asillustrated. In some embodiments, the method includes formatting theserialized audio bits with a digital start code and inserting theserialized audio bits and the digital start code into a blanking periodof the digital video data, thereby generating a combined digital audioand video signal. Some embodiments include converting, by adigital-to-analog converter (DAC), the combined digital audio and videosignal to analog, thereby generating a combined analog audio and videosignal including an audio data stream in a native form and transmittingin one direction the combined analog audio and video signal to areceiver. The method can include receiving, at the receiver, thecombined analog audio and video signal and converting, by an ADC, thecombined analog audio and video signal to a combined digital audio andvideo signal. Such method includes extracting, utilizing an audiodecoder, the audio data stream from the combined digital audio and videosignal. In some embodiments, the method includes the video decoderproviding timing information and location of the video blanking periodto aid the searching for audio data by the audio decoder.

Another aspect of the one or more embodiments may include a method oftwo-way audio transmission, such that in addition to the transmissionfrom the transmitter to the receiver as previously described, and thesampled audio signal being sampled at a first frequency, wherein thetransmitter includes an opposite direction audio signal receiver, andwherein the receiver includes an opposite direction audio signaltransmitter. With such a two-way configuration, there are included thesteps of receiving, at the opposite direction audio signal transmitterincluded within the receiver, a second audio signal; determining, by thearbiter of the opposite direction audio transmitter and the videodecoder of the receiver, one or more vertical blanking lines of thesecond digital video signal and one or more time slots within the one ormore vertical blanking lines without audio data; sampling, by anotheranalog-to-digital converter (ADC) disposed within the opposite directionsignal transmitter, the second audio signal at a second frequency if thesecond audio signal is an analog audio signal; storing, in anotherFirst-in-First-Out (FIFO) buffer disposed within the opposite directionsignal transmitter, second digitized audio samples corresponding to thesecond audio signal, which may be either the second audio signal if indigital form or the second digitized samples of the second (analog)audio signal; inserting start pattern and one or more second serializedaudio data and/or end pattern into a vertical blanking interval of thecombined analog audio and video stream; and transmitting, by theopposite direction signal transmitter disposed within the receiver tothe opposite direction signal receiver disposed within the transmitter,an audio stream corresponding to the start and/or end patterns and theone or more second serialized audio bits to the transmitter thatincludes the audio receiver, wherein the transmitting of the audiostream occurs of the single cable in another direction opposite the onedirection. It is noted that the audio data inserted can be one ormultiple insertions per line.

The opposite direction audio signal receiver within the transmitter usesa clock frequency that needs to only be substantially the same as thefrequency used by its corresponding opposite direction audio signaltransmitter within the receiver, as a pair. It can be different than thefrequency used by the opposite direct ion. When the video decoder on thereceiver side decodes video correctly, both sides should preferably havethe same video line information including sync, blanking, active videolocation. The method includes extracting the serialized audio data basedon the one or more vertical blanking lines and one or more time slotsand storing the extracted audio samples in a FIFO buffer. In someembodiments, the method includes utilizing predetermined clockfrequencies which are substantially the same as the opposite audiotransmitter clock frequency that is within the (video) receiver. Themethod includes, at the opposite direction audio signal receiver withinthe (video) transmitter, selecting an output sample frequency based on atransmission side clock frequency and retrieving the audio samples andoutputting a reconstructed audio stream based on the output samplefrequency. In some embodiments, the audio clock is set to a frequencysubstantially the same as the audio clock frequency used in thetransmitter side (e.g., 8 KHz, 16 KHz, and the like). Output audiosamples are extrapolated from the data stored in the FIFO buffer basedon the difference between clocks for obtaining equal spaced audio datamatching the receiver audio clock.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and features of embodiments described hereinwill become apparent to those ordinarily skilled in the art upon reviewof the following description of specific embodiments of the invention inconjunction with the accompanying figures, wherein:

FIG. 1 illustrates a block diagram of an exemplary audio transmitter inaccordance to one or more embodiments of the invention;

FIG. 2 illustrates a schematic diagram for an output analog video signalin accordance with one or more embodiments of the invention;

FIG. 3 illustrates a block diagram of an exemplary audio receiver inaccordance with one or more implementations;

FIG. 4 illustrates a flow chart of a method of transmitting an audiosignal data in accordance to one or more embodiments of the invention;

FIG. 5 illustrates a flow chart of a method of receiving an analog videosignal in accordance with one or more embodiments of the invention;

FIG. 6 illustrates a block diagram of an exemplary video transmitter inaccordance to one or more embodiments of the invention;

FIG. 7 illustrates a block diagram of an exemplary video receiver inaccordance to one or more embodiments of the invention;

FIG. 8 illustrates a schematic diagram for an analog video and audiosignal in accordance with one or more embodiments of the invention;

FIG. 9 illustrates a block diagram of an exemplary video receiver thatincludes opposite direction audio signal transmitter in accordance toone or more embodiments of the invention;

FIG. 10 illustrates a block diagram of an exemplary video transmitterthat includes an opposite direction audio signal receiver in accordanceto one or more embodiments of the invention; and

FIG. 11 illustrates a schematic diagram for an analog video and audiosignal in accordance with one or more embodiments of the invention.

FIG. 12 illustrates the interpolation between the incoming sample rate Fand the output sample rate F′.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in detail with reference tothe drawings, which are provided as illustrative examples of theinvention so as to enable those skilled in the art to practice theinvention. Notably, the figures and examples below are not meant tolimit the scope of the present invention to a single embodiment, butother embodiments are possible by way of interchange of some or all ofthe described or illustrated elements.

Moreover, where certain elements of the present invention can bepartially or fully implemented using known components, only thoseportions of such known components that are necessary for anunderstanding of the present invention will be described, and detaileddescriptions of other portions of such known components will be omittedso as not to obscure the invention.

Embodiments described as being implemented in software should not belimited thereto, but can include embodiments implemented in hardware, orcombinations of software and hardware, and vice-versa, as will beapparent to those skilled in the art, unless otherwise specified herein.In the present specification, an embodiment showing a singular componentshould not be considered limiting; rather, the invention is intended toencompass other embodiments including a plurality of the same component,and vice-versa, unless explicitly stated otherwise herein. Moreover,applicants do not intend for any term in the specification or claims tobe ascribed an uncommon or special meaning unless explicitly set forthas such. Further, the present invention encompasses present and futureknown equivalents to the known components referred to herein by way ofillustration.

FIG. 1 illustrates an audio encoder system 100 on the transmitter sidewhere an embodiment is applicable. As shown in FIG. 1, system 100includes analog-to-digital converter (ADC) 104, buffer 106, arbiter 108,video encoder 110, signal combiner 112 and digital-to-analog converter(DAC) 114. In an exemplary embodiment, system 100 is configured toreceive a continuous analog audio signal 102 and process analog audiosignal 102 for transmission along with video signal 111, via a singletransmission line.

In one embodiment, ADC 104 may be configured to receive audio signal 102in analog or digital form, and if in analgo form, then sample analogaudio signal 102 at a predetermined frequency. In one embodiment, theaudio sampling rate may be set at less than a video line rate of videosignal 111, doing so may prevent overflow in buffer 106. ADC 104 may beconfigured to output quantized audio data 103 corresponding to thesampled analog audio signal 102, which is needed when the audio signalis in analog form, but not when the analog signal is in digital form, aswell be well understood. In one embodiment, ADC 104 may be configured tosample audio signal 102 at 8 kHz. In another embodiment, ADC 104 may beconfigured to sample audio signal 102 at 16 kHz. In yet anotherembodiment, ADC 104 may be configured to sample audio signal 102 at 32kHz.

In some embodiments, ADC 104 may be configured to receive an analogaudio signal 102, sample and quantize the analog audio signal 102 indigital format resulting in quantized audio data 103. In someembodiments, buffer 106 may be configured for buffering quantized audiodata 103. Buffer 106 may be configured to receive quantized audio data103 from ADC 104 and store entries until a video blanking period becomesavailable, which is discussed in further detail below, and may also beconfigured to directly receive various portions of the digital audiosignal. In one embodiment, buffer 106 may include a first-in-first-out(FIFO) buffer configured to not alter the order in whichquantized/digital audio data is received and transmitted by buffer 106.In another embodiment, buffer 106 may be configured to timestampincoming quantized/digital audio data. In one embodiment, in response tobuffering quantized audio data 103, buffer 106 may be configured tonotify arbiter 108 that quantized/digital audio data is available inbuffer 106. In one embodiment, buffer 106 may be configured to includeinterrupt I/O circuitry in communication with arbiter 108. In anotherembodiment, arbiter 108 may include polling I/O circuitry configured topoll buffer 106 to determine the presence of quantized/digital audiodata 103 in buffer 106.

In some embodiments, arbiter 108 analyzes video signal 111 to determinethe timing and presence of the video blanking interval of video signal111, which is discussed in further detail below. In one embodiment, inresponse to the polling and/or interrupt, arbiter 108 may be configuredto determine the availability of a video blanking period (not shown inFIG. 1) of video signal 111. In one embodiment, video signal 111includes a blank interval and at least one portion of video datadisposed therein. In one embodiment, the video blanking interval mayinclude a horizontal sync pulse, a vertical sync pulse, a color syncpulse, and/or other data corresponding to video data of video signal111. In another embodiment, the video blanking interval does not containany sync pulses and/or other data corresponding to video data of videosignal 111, and arbiter 106 or the video encoder 110 may be configuredto insert sync pulses in a predetermined location of the video blankinginterval based on a predefined video format, which is discussed infurther detail below.

In some embodiments, in response to determining the timing and presenceof the video blanking interval, arbiter 108 may be configured to commandbuffer 106 to transmit quantized audio data 103 corresponding to theavailability of a video blanking period of video signal 111. When buffer106 does not contain data entries (i.e., quantized audio data 103) atthe time of determining the presence of the video blanking interval, therow will be skipped until there are entries stored in buffer 106. In oneembodiment, arbiter 108 may include synchronization circuitry includingone or more clocking circuits that processes video signal 11 l andperforms task management protocol for interleaving quantized audio data103 with the video blanking period of video signal 111. In oneembodiment, arbiter 108 may be configured to fetch or retrieve thequantized audio data from buffer 106.

In one embodiment, arbiter 108 may be configured to receive digitalvideo signal 111 from video encoder 110. Arbiter 108 may be configuredto check for the availability of quantized/digital audio data 103 storedin buffer 106 in response to approaching the blank interval time ofvideo signal 111. In response to determining that quantized/digitalaudio data 103 is available in buffer 106, arbiter 108 may generate oneor more sync pulses, one or more quantized audio pulses corresponding toquantized/digital audio data 103 stored in buffer 106, and an audioheader describing the one or more quantized audio pulses. For example,the sync pulse generation may be performed by the video encoder 110,while arbiter 108 may determine when to insert the audio data and formatthe data accordingly. In one embodiment, the header may indicate thepresence of audio data and may be utilized for decoding audio on areceiver end, which is discussed in further detail below. In otherembodiments, in general, the sync pulses generation is by the videoencoder (encoder). The arbiter determines when to insert the audio dataand format the data accordingly. It is understood that the term “insert”or “inserting” when used herein should be broadly interpreted to includesuperimposing, combining, injecting or other manners of including asignal and/or its components, such as combining the audio signal withthe existing combined audio video stream.

In one embodiment, video encoder 110 may be configured to generatedigital video signal 111, and output video signal 111 to arbiter 108 andsignal combiner 112. In another embodiment, video encoder 110 may relayan existing video signal received from a video source (not shown). Insome embodiments, video encoder 110 may be configured to output videosignal 111, which may be configured as 8-bit, 10-bit or 12-bit 4:4:4 or4:2:2 YUV data. For example, in some embodiments, due to having a singlecable, the UV data may be modulated before adding to the Y and sync toform one digital data before converting to analog. In other embodiments,YUV data may be interleaved in a predefined way together with syncbefore the DAC conversion. In some embodiments, video signal 111 may beconfigured using other sub-sampled formats. In some embodiments, videoencoder 110 may include one or more analog processors, chrominanceprocessor, luminance processor, clocking circuitry, and a hostcommunication interface (not shown in FIG. 1).

As discussed above, arbiter 106 may be configured to determine theavailability of a video blanking period of video signal 111. In someembodiments, arbiter 106 may include processing circuitry and memorystoring firmware and/or other types of non-transitory computer readableinstructions thereon. Arbiter 106 processing circuitry may be configuredto execute instructions contained in the firmware and/or memory forimplementing the exemplary embodiments described herein. In someembodiments, processing circuitry within arbiter 106 may include one ormore hardware processors, one or more field programmable gate arrays(FPGA), alone and/or in combination.

In one embodiment, arbiter 106 may be configured to manage timing forinterleaving and/or inserting quantized/digital audio data 103 stored inbuffer 106 with video signal 111 via clocking functionality (not shownin FIG. 1). In some embodiments, arbiter 106 may include clockingfunctionality for synchronizing quantized/digital audio data 103 withvideo signal 111. Arbiter 106 may include one or more digital signalprocessors (DSP), field programmable gate arrays (FPGA) and orapplication specific integrated circuits (ASIC). In one embodimentclocking circuitry of arbiter 108 may include one or more of phaselocked loop (PLL) clock, a non-PLL clock, a quartz crystal oscillator,and LC resonance tank circuit, alone and/or in combination. Clockingcircuitry may include additional timing and signal conditioningfunctionality including, for example, fan-out buffers, multipliers anddividers, synthesizers, alone and/or in combination.

As shown in FIG. 1, signal combiner 112 may be configured to receivequantized audio data 103 from buffer 106 and digital video signal 111from video encoder 110. Signal combiner 112 may be configured tointerleave quantized/digital audio data 103 in the video blanking periodof video data 111, which is described in further detail below. In oneembodiment, signal combiner 112 may be configured to interleavequantized/digital audio data 103 with video signal 111 by insertingquantized/digital audio data 103 into the video blanking portion ofvideo signal 111, and output a combined audio and video (A/V) digitalsignal 113 to digital-to-analog converter (DAC) 114.

In some embodiments, DAC 114, may include an 8 bit DAC, a 10 bit DAC, orof any higher bit width and operating at a specific frequency asrequired by video signal 111. For example, DAC 114 may run at 148.5 MHz,which is two times an input data rate of a standard HD digital video(e.g., 1080p30/25 and 720p60/50). In some embodiments, the amplitude ofthe DAC output signal can be set by an external current setting resistor(not shown in FIG. 1). DAC 114 may be configured to receive A/V signal113 from signal combiner 112 in digital format, convert combined audioand video signal 113 to analog format, and output an analog audio andvideo (AV) signal 116 for transmission via a single transmission line(not shown in FIG. 1). In one embodiment, the signal transmission linemay be a coaxial cable configured to transmit analog signal via one ormore fiber optic cables and/or twisted pair wire transmission lines.

In one embodiment, video signal 111 may include a resolution of1280×720p. Video blanking interval 210 may correspond to the videoblanking period of a 1280×720P video signal. Video signal 111 mayinclude streaming video frames, each frame including 1650 pixels perline with 1280 active video pixels. In one embodiment the blank intervalof video signal 111 includes 370 pixels configured to contain thehorizontal sync pulse, color sync pulse, and/or other data correspondingto the video data.

In one embodiment, for example, video signal 111 may correspond to theSMPTE 296M standard, wherein a 1280×720P video frame has 750 horizontallines or rows, of which 30 lines are a vertical blanking interval thatdo not contain video data. According to the numbering scheme of SMPTE296M, lines 26-745 are active video frame data. Both active frames andvertical blanking intervals may include a respective video blankinginterval 210. The video blanking interval may be the same size for eachrow of video signal 111 due to the periodic nature of the video blankinginterval. In other embodiments, video signal 111 may correspond to otherSMPTE standards including but not limited to: 259M, 344M, 292M, 372M,424M, ST-2081, ST-2082, and/or ST-2083. It should be noted that theexemplary embodiments described herein are not limited to the linenumbering scheme as described above. A person of ordinary skill in theart can apply the principal of the invention to any other numberingscheme after reading the disclosure provided herein.

In some embodiments, arbiter 108 in conjunction with signal combiner 112may be configured to generate one or more quantized audio pulses (notshown in FIG. 1) corresponding to the one or more of the plurality ofquantized audio data 103 stored in buffer 106. In the digital domain,this generating quantized audio pulses corresponds to digital datalasting the duration of the pulse. Arbiter 108 in conjunction withsignal combiner 112 may also generate an audio header corresponding toone or more quantized audio pulses (not shown in FIG. 1). In someembodiments, arbiter 108 may be configured to cause buffer 106 totransmit the audio header to signal combiner 112, along with quantizedaudio data 103, for multiplexing into combined A/V signal 113. In oneembodiment, signal combiner 112 and arbiter 108, may utilize timedivision multiple access (TDMA) multiplexing protocol in order tocombine quantized audio data 113 and video signal 111, which isdescribed in further detail below.

Referring now to FIG. 2 in conjunction with FIG. 1, FIG. 2 illustratesan exemplary A/V signal 216 according to one or more embodiments. A/Vsignal 216 may correspond to A/V signal 116 of FIG. 1. In someembodiments, A/V signal 216 depicted in FIG. 2 may correspond to asingle active row of a single video frame of video signal 111. As shownin FIG. 2, A/V signal 216 may include video data 211 and video blankinginterval 210. Video data 211 may correspond to video data of videosignal 111 generated or received by video encoder 110, as discussedabove. Video blanking interval 210 of combined A/V signal 116, 216 mayinclude one or more audio pulses 213, audio header 215, and sync pulse216. As shown in FIG. 2, video blanking interval 210 may exist beforeand after sync pulse 216. In some embodiments, sync pulse 216 mayinclude a horizontal sync pulse, vertical sync pulse, color sync pulse,and/or other data corresponding to CODEC of video signal 116, 216.

In some embodiments, arbiter 108 may be configured to determine a syncpulse location of a sync pulse 216 in the video blanking interval 210.Arbiter 108 may be configured for identifying, without calculating, atleast one permissible portion of the blank interval corresponding to afirst duration exceeding a predetermined duration of the audio headerand the one or more quantized audio pulses.

In another embodiment, arbiter 108 may be configured for identifying,without calculating, a sync portion configured to include one or moresync pulses based on a pre-defined video standard, the sync portiondiffering from the at least one permissible portion of the blankinterval. In some embodiments, A/V signal 216 may include sync pulsesand/or other data corresponding to video data 211 in video blankinginterval 210. In one embodiment, identifying a sync pulse location mayinclude digitizing an existing analog video signal (e.g., via ADC 104)and identifying the sync pulse location and blanking intervals from thedigitized video stream.

In another embodiment, video signal 111 may include a pre-defineddigital format having a video blanking interval that is devoid of syncpulses, and identifying the sync pulse locations may includecommunication between video encoder 110 and audio arbiter 108 regardingwhere (i.e., a temporal location) sync pulses 216 will be insertedaccording to the pre-defined video standard. For example, video encoder110 may combine or modulate active YUV video data and includesynchronization data to form a single video data stream fortransmission. In some embodiments, arbiter 108 may include an audioencoder and/or a video encoder (not shown) having a pixel counter.Utilizing the pixel counter, arbiter 108 may identify insertionlocations for sync and audio data that are predefined based on the countvalue of the pixel counter.

In one embodiment, because the transmission of digital video signal indigital format does not require sync or color sync data, identifying thesync pulse location and blank intervals portions that are devoid of syncpulses may include communication between the video encoder (e.g.,combiner 112) and audio arbiter 108 regarding where the sync pulse 216will be inserted according to a pre-defined video standard. Thus,determining a sync pulse location may include determining one or moreportions of video blanking interval 210 that is/are free of any videorelated signals corresponding to video data 211 (e.g.horizontal/vertical/color sync pulse and/or other data corresponding tovideo data 211). Analog video transmission, however, includes syncpulses and digitizing the analog video stream (e.g., via ADC 104) mayidentify the temporal location of sync pulses present in video data 211.In another embodiment, arbiter 108 may be configured to determine alocation of other data in the blanking interval (e.g.,horizontal/vertical/color sync pulse and/or other data corresponding tovideo data 211) based on a predefined video format.

In some embodiments, video blanking interval 210 may include audioheader 215 and one or more quantized audio pulse(s) 213. A singlequantized audio pulse 213 may correspond to one digitized audio data(e.g., in 8/10/12/16 bit format) stored as one buffer entry. The levelof audio pulse 213 (i.e. amplitude or voltage level) may linearlyrepresent the digital data corresponding to quantized/digital audio data103 stored in buffer 106. In one embodiment, for example, in the case ofan 8-bit sample data, 00hex may include the lowest level of audiopulse(s) 213 and FFhex may include the highest level of audio pulse(s)213. In some embodiments, other hexadecimal leveling protocol may beutilized for various video formats without diverting from the scope ofthe present embodiments described herein. In some embodiments, theduration of quantized/digital audio pulse(s) 213 may be pre-definedbased on the particular video format of signal 116, 216.

As shown in FIG. 2, audio header 215 and quantized/digital audio pulses213 each include a predetermined pulse duration (i.e., pulse width).Audio pulses may be distorted at the far end (i.e., receiver side) ofthe cable due to imperfect frequency response, thus pulse duration mustbe chosen accordingly. In some embodiments, the duration of each audiopulse 213 may be programmable and predetermined for each video formatbased on the blank space available and the cable length. Each videoblanking interval 210 of signal 216 may have the same size/duration dueto the periodic nature of the video blanking interval in each row ofevery frame of video signal 216. Thus, the duration or pulse width ofquantized/digital audio pulses 213 and audio header 215 may bepre-defined for certain video formats in a manner such that at least oneaudio header 215 and one quantized/digital audio pulse 213 duration canfit in blanking interval 210. In some embodiments, based on theparticular pre-defined video format, the duration of audio header 215and quantized/digital audio pulses 213 are selected such that videoblanking interval may include at least two quantized/digital audio datapulses 213.

For example, some video formats (e.g., SMPTE standards discussed above)may include a wider video blanking interval that provides sufficientspace for more than one quantized/digital audio pulse 213. In someembodiments, in order to accommodate inserting two or morequantized/digital audio pulses 213 in each blanking interval 210, thepulse duration of quantized/digital audio pulses 213 and/or audio header215 may be selected more narrowly, based on the duration of videoblanking interval 210 of the particular video format. Doing so mayincrease the transfer data rate when two or more audio pulses 213 can beinserted into video blanking interval 210.

As discussed above, quantized/digital audio pulses 213 may include ananalog representation of quantized audio data 102 stored in buffer 106in reference to the header level of audio header 215. In someembodiments, audio header 215 may include a maximum signal value or amid-level signal value of audio quantized audio pulses 213. In oneembodiment, audio header 215 may be configured to serve as a flag toindicate valid audio data and as a reference level to decode quantizedaudio pulses 213 and reconstruct audio data to an original format by adownstream receiver, which is discussed in further detail below in thediscussion of FIG. 3

In one embodiment, audio header 215 may correspond to a voltage levelthat is distinct from video blanking interval 210 and may be readilyidentified by a downstream audio receiver. The voltage level of audioheader 215 may be configured to be readily differentiated in videoblanking interval 210 and facilitates the determination by a downstreamreceiver that a particular video blanking interval 210 contains no audiodata. In one embodiment, audio header 215 includes a zero audio level oran integer multiple of a zero audio level. The audio header may serve asa zero reference for decoding quantized audio pulses 213 into abi-directional AC wave. In some embodiments, the one or more quantizedaudio pulses 213 are superimposed (i.e. interleaving or multiplexing)with a DC offset.

In one embodiment, audio header 215 may correspond to the DC offsetduring transmission, wherein audio header 215 may be utilized forrecovering the DC offset in a downstream video receiver. Duringtransmission of signal 216, the voltage level of audio pulses 213 canchange for various reasons. The quantization level on a receiver sidemay also be different than the original DAC conversion level. Therefore,two distinct levels are needed to accurately recover the audio digitalvalue of audio pulses 213. Thus in some embodiments audio header 215 maycorrespond to a predefined header level and the video blank level forreference to scale the received audio level accordingly. Thus, in someembodiments, audio header 215 may contain a DC offset plus a value thatis half or full amplitude of the audio signal to aid the decoding by adownstream transmitter, for example, as discussed in FIG. 3A below.

In some embodiments, arbiter 108 in communication with signal combiner112 may be configured to interleave audio header 215 and one or moreaudio samples (or portions if digital) 213 at a predetermined time invideo blanking interval 210. In one embodiment, interleaving may includemultiplexing, in the permissible portion of blank interval 210, audioheader 215 and one or more audio pulse(s) 213, with the at least oneportion of video data 211 resulting in a combined audio and video signal216 that represents at least a portion of the audio and video data.While FIG. 2 depicts audio header 215 and audio samples 213 locatedbetween video data 211 and sync pulse 216, in some embodiments, header215 and audio samples(s) 213 may be inserted before or after sync pulse216. In some embodiments, audio header 215 and audio samples 213 may beincluded both before and after sync pulse 216.

Referring now to FIG. 3, in conjunction with FIGS. 1 and 2, FIG. 3depicts an exemplary audio decoder system 300 corresponds to the audioencoder system 100 of FIG. 1. Audio decoder system 300 in conjunctionwith audio encoder system 100 may comprise an audio/video CODEC system.Decoder system 300 may include ADC 302, audio detection module 304,audio extractor module 306, and FIFO buffer 303. As shown in FIG. 3, ADC302 may be configured to receive A/V signal 116, 216, 316 in analogformat and convert analog A/V signal 116, 260, 316 into the digitaldomain. ADC 302 may be configured to output A/V signal 116, 216, 316 indigital format as a digital A/V signal 313. ADC 302 may be configured tooutput A/V signal 313 to audio detection module 304, audio extractorarbiter 306, and a video destination (not shown in FIG. 3). In someembodiments, decoder system 300 may be configured to receive an analogvideo signal 116, 216, 316 including audio header 215 and quantizedaudio pulses 213 that was placed in a video blanking interval 210 of theanalog video signal 116, 216, 316 based upon a predetermined samplingfrequency.

In some embodiments, audio extractor arbiter 306 may include a videodecoder sync slicer (not shown in FIG. 3). Detecting the presence of anaudio header may include utilizing information from the sync slicerfunction of a video decoder to aid the detection of audio header 215 atone or more predefined locations/time intervals according to the videotransmission protocol and resolution of A/V signal 313. In oneembodiment the sync position detection may provide a predeterminedsearch range for detecting the presence of an audio header. The searchrange may include a time interval of video signal 111 which includes thevideo blanking interval. In other embodiments other functionality of thevideo decoder may aid in the detection of audio header 215.

In some embodiments, audio detection module 304 may be configured todetect the presence of audio header 215 contained in video blankinginterval 210. In response to detecting audio header 215, audio detectionmodule 304 may be configured to communicate the presence of audio datato the audio extractor arbiter 306. In response, audio extractor arbiter306 may be configured to extract audio samples 213 from video blankingportion 210, by extracting the digitized AV sample 313 at predeterminedtiming intervals corresponding to the location of header 215 detected byaudio detection module 304. In some embodiments, audio extractor arbiter305 may be configured to convert the extracted audio data, back to anoriginal value with reference to the header level of header 215. In oneembodiment, audio extractor 305 utilizes the header level for recoveringa DC offset value added onto the quantized audio data 103 duringtransmission. Doing so will prevent the quantized audio data from beingidentified as a horizontal sync signal as the signal swings low. Next,audio extractor 306 may be configured to transmit the restored audiodata samples to buffer 303 for later retrieval. In one embodiment, Audioextractor 306 may include a local audio clock encoder (not shown in FIG.3) with substantially the same corresponding audio sampling frequency asadopted on the transmitter side. Substantially the same means thedifference is negligible. In some embodiments, reconstructing thecontinuous audio signal includes using a predetermined audio samplingrate corresponding to a sampling rate of an upstream audio encoder(e.g., audio encoder system 200). It is noted that the nomenclature of“upstream” and “downstream” is used for illustrative purposes, andspecifically indicative of a particular direction.

In one embodiment, audio extractor 306 may include clockingfunctionality for synchronizing the reconstruction of audio data. Audioextractor arbiter 306 may include one or more digital signal processors(DSP), field programmable gate arrays (FPGA) and or application specificintegrated circuits (ASIC). In one embodiment clocking circuitry ofaudio extractor arbiter 306 may include one or more of phase locked loop(PLL) clock, a non-PLL clock, a quartz crystal oscillator, and LCresonance tank circuit, alone and/or in combination. Local audio clockcircuitry of audio extractor arbiter 306 may include additional timingand signal conditioning functionality including, for example, fan-outbuffers, multipliers and dividers, synthesizers, alone and/or incombination. Local audio clock may be utilized for retrieving audio datafrom FIFO buffer 306 in a periodic fashion to reconstruct the originalaudio signal in digital format and output a continuous audio signal 303.However, due to different clock references of the transmitter andreceiver clocks, some clock frequency difference may be present causingvariation in sampling frequency between the transmitter and receiver,which may require correction.

In some embodiments, the receiver reconstruction clock frequency shouldbe substantially same as the transmitter sampling clock frequency.Substantially same means any difference is negligible. For example,these differences are due to both receiver and transmitter have theirindependent clock reference. Even though the specified frequency is thesame on both sides, however, due to the free running nature of theseclocks, they cannot be the same or synchronized.

In some embodiments, in the case that the transmitter sampling frequencyand receiver sampling frequency are not substantially the same,interpolation of the received data may be performed to reconstruct theoriginal audio signal at the receiver's sampling rate and to preventFIFO buffer overrun or underrun over times due to the difference insampling frequency. As such, the FIFO buffer size can be reduced.Interpolation, also referred to as rate matching, in this mannereliminates the need for complicated and resource intensivesynchronization of audio and video signal, and also eliminates the needto consider the video frame boundary. Interpolation, according to one ormore embodiments, also does not require calculating and buffering theaudio data based on the frame periodicity. Rather, the difference insampling frequencies between the transmitter and receiver can becorrected by interpolating the received audio samples according to thedifferences (e.g., frequency difference between receiver andtransmitter).

Referring now to FIG. 4, FIG. 4 depicts a flowchart of an exemplarymethod 400 in accordance with one or more exemplary implementationdescribed herein. Method 400 may begin at an operation 402, receiving anaudio signal, which may be analog or digital in form. At an operation404, quantizing the analog audio signal in digital format, or receivingthe digital portion. At an operation 406, buffering one or morequantized audio data. At an operation 408, receiving a video signalcomprising a blank interval and a video interval. At an operation 410,combining, an audio header and at least a portion of the buffered audiodata in the blank interval of the video signal. The method may concludeat an operation 412, converting the combined digital audio/video signalto analog and transmitting the combined audio/video signal comprisingthe audio header and at least the portion of the buffered audio data adownstream video receiver wherein the header data is detected andextracted and utilized to restore the audio signal.

Referring now to FIG. 5, FIG. 5 depicts a flowchart of an exemplarymethod 500 in accordance with one or more exemplary implementationdescribed herein. Method 500 may begin at an operation 502, receiving ananalog video signal, the analog video signal including one or more audioheaders, and one or more quantized audio pulses corresponding toquantized audio data or digital data portions. For example, each of theone or more audio headers are followed by one or more quantized audiopulses during the video blanking time. At an operation 504, detectingthe audio header in a blank interval of the analog video. At anoperation 506, determining a reference level of the audio header. At anoperation 508, extracting, in response to detecting the audio header,the one or more quantized audio pulses. At an operation 510, convertingthe one or more quantized audio pulses to an original value of the oneor more quantized audio data based on the reference level of the audioheader. At an operation 512, storing the one or more of the quantizedaudio data in the original value in a First-in-First-Out (FIFO) buffer.The method may conclude at an operation 514, reconstructing, utilizingthe FIFO buffer, local audio clock and an extrapolator a continuousaudio signal from the one or more of the quantized audio data in theoriginal value.

As discussed above, FIGS. 1-5 describe some embodiments whereindigitally sampled audio data or digital audio data is converted to ananalog voltage level. The analog voltage level is set proportional tothe digital sample value and superimposed onto the analog video signalat predefined time slot in the horizontal blanking period preceded by astart pulse. However, due to the limited resolution of the DAC(digital-to-analog converter) on the transmitter side and limitedresolution of the ADC (analog-to-digital converter) on the receiverside, the dynamic range or SNR (signal-to-noise ratio) that can beachieved is also limited. This results in poor SNR and background noiseon the audio channel performance. Improving audio performance may beachieved by utilizing high resolution (14-bit and over) DAC and ADC. Yetthis approach is resource intensive. However, transmitting audio sampledata in a native digital format, in accordance with one or moreembodiments described herein, may alleviate SNR, thus achieving highquality audio channel performance, while also conserving resources.

Referring now to FIGS. 6-7, in conjunction with FIG. 1 and FIG. 3, FIGS.6-7 depict a transceiver system having video transmitter 600 and videoreceiver 700, respectively. For example, FIG. 6 may be similar to FIG.1, however, different in that the data output from the arbiterrepresenting analog or digital pulses data. Video transmitter 600 andvideo receiver 700 block diagrams may be similar to transmitter/receiver100, 300 as depicted in FIG. 1 and FIG. 3, wherein similarly labeledparts and ones and tens level numbers correspond to similar structureshaving similar functionality. Instead of analog level representation asdescribed in FIGS. 1-5 above, transmitter/receiver 600, 700 areconfigured for transmitting audio data over a video signal by way ofsending audio data in a native digital form (e.g., 12 bit or 24 bitserial digital data stream). For example, in some embodimentscorresponding to voice grade audio, 13 to 16 bits are typicallysufficient. In other embodiments having high definition audio, 24 bitsmay be utilized.

In some embodiments, video transmitter 600 (also referred to simply as“transmitter”) may include ADC 604, FIFO 606, arbiter 608, videoformatter 610, combiner 612, and DAC 614. As shown in FIG. 6, ADC 604receives analog audio signal 602 and clock signal 607 as input. Clocksignal 607 may correspond to a phase-lock-loop (PLL) configured forproviding clock functionality (e.g., PLL 605). In some embodiments, PLL605 may be part of video transmitter 600, or may be separated from, andin wireless communication with, video transmitter 600. For example, insome embodiments, video transmitter 600 may be configured to receiveclock signal 607 from an external source (not shown). Clock signal 607operates at a frequency Fs. In some embodiments, Fs. may include: 8, 16,32, 44.1, 48 or 96 KHz.

In some embodiments, an operation of video transmitter 600 may includereceiving, as input, analog audio signal 602 by way of ADC 604 ordigital audio signals. ADC 604 performs sampling of analog audio signal602 periodically at the rate of Fs, based on the sampling clock signal607. The sampled audio data or the digital audio data is thentransmitted to FIFO 606 for storage in chronological order. Since theextracted audio data samples may not come in periodically, FIFO buffer606 also facilitates the non-periodic insertion of audio samples. Forexample, the audio signal can be sampled periodically at the rate of Fs.The FIFO buffer then actually facilitates the non-periodic insertion ofaudio samples onto the video blanking time available for audio slot.(The video row period is not synchronized with the Fs. Some of thevertical blanking rows are reserved for other data communication and notavailable for audio transmission). FIFO buffer 606 outputs stored audiosamples in response to command signals from arbiter 608.

In some embodiments, arbiter 608, utilizing timing signals 611, checksfor the availability of audio data samples stored in FIFO buffer 606 andchecks for the availability of video blanking period from the videoencoder/formatter. Checks for the availably of audio data stored in FIFObuffer 606 may be implemented by command signals including, for example,a polling/calling function of arbiter 608. Arbiter 608 may read/callaudio data stored in FIFO buffer 606 and formats the digital audio datafor transmission over the blanking time thereby outputting digital audiostream 609. Formatting audio data for producing digital audio stream 609may include generating a start code header in serial bit format.

In some embodiments, similar to that as shown and described in FIG. 1,video formatter 610 may receive as input video-in signal 603 and outputdigital video signal 613 to combiner 612. As discussed above, videoformatter 610 communicates timing signals 611 to arbiter 608. Forexample, in some embodiments arbiter 608 formats audio packets by addingdigital audio header and serialized audio data bit stream following apredefined format, or it can also be digitally encoded or appended withredundancy bits for the purpose of error checking and correction toimprove the reliability of the transmission in the presence of noise.Each bit of the stream is a number of same digital data byte/code thatrepresents the height and duration of the digital bit pulse whenconverted to the analog domain. This is similar to the audiotransmission except that the pulse height is typically fixed since theaudio data information is transmitted digitally as 1/0 bit stream athigher speed instead of the variable height pulses at lower speed. Eachvariable height pulse in analog transmission is equivalent to a seriesof 13-16 1/0 shorter pulses in digital transmission, plus optionalredundancy bits.

Together with the start code header, digital audio stream 609 may becombined by superposition with digital video signal 613, via combiner612. Superimposing digital audio stream 609 may be implemented byutilizing timing signals 611 and implementing time division multiplexing(TDMA). For example, timing signal 611 facilitate sending digital audiostream 609 at mutually exclusive time slots. Combined digital audio andvideo data 615, containing both audio and video data in the digitaldomain, is then converted to analog domain by DAC 614. Thus, DAC 614outputs analog audio and video (A/V) stream 616 for downstreamtransmission to video receiver 700.

Referring now to FIG. 7, FIG. 7 depicts video receiver 700 (alsoreferred to as simply “receiver”) in accordance with some embodimentsdescribed herein. As shown in FIG. 7, video receiver 700 includes ADC704, audio extractor 708, FIFO buffer 706, data synchronizer 712, andvideo decoder 710. Video receiver 700 receives as input analog A/Vstream 616, via ADC 704. Analog A/V stream 616 containing both audio andvideo data is converted back to digital domain by ADC 704. Afterconverting analog A/V stream 616 to the digital domain, ADC 704 outputsA/V stream 616 to audio extractor 708 and video decoder 710.

Video decoder 710 receives A/V stream 616 via ADC 704 and decodes andoutputs the baseband video signal (YUV) 713 for display to the user.Video signal 713 corresponds to the original video-in signal 603. Videodecoder 710 communicates timing signals 711 to audio extractor 708. Insome embodiments, video decoder 710 may utilize time divisionmultiplexing access to process and output digital video signal 713.Video decoder 710 decodes the video signal and provides the necessarytiming information to audio extractor 708. In some embodiments,extractor 708 may be separated into audio (header) detector andextractor similar to the analog counterpart. Based on timing signalsprovide by video decoder 710 and the detected digital audio header,audio extractor 708 extracts audio data from A/V stream 616 and outputsaudio data to FIFO buffer 706.

Since the extracted audio data samples does not come in periodically dueto the fact that the period of the video blanking (i.e. video lineperiod) is not the same as the audio sample period, extracted audiosamples may be stored in FIFO buffer 706. FIFO buffer 706 outputs storedaudio data to synchronizer 712. In some embodiments, synchronizer 712receives PLL 705 clock signal having a signal frequency (Fs′) atsubstantially the same rate as clock 605, frequency (Fs). As discussedabove, transmitter and receiver are typically located remotely from eachother with connection only by one video cable. This is desirable toreduce cost and increase efficiency so that only a single low cost cableis needed to route between transmitter (e.g., camera) and receiver(e.g., display/recorder). Each side has its own free running referenceclock and cannot be guaranteed to have exactly the same frequency andphases or synchronized. Therefore, only substantially the same frequencycan be expected. Even though both sides are running at 8 KHz, they willnot be the same. In some embodiments, synchronizer 712 retrieves audiodata samples stored in FIFO buffer 706 and calculates the correct dataat its output based on signal Fs′ Based on the corrected output data,data synchronizer 712 outputs a digital audio stream 716. In someembodiments, calculating correct data at the output is performed byextrapolation from adjacent samples based on constantly tracking thedifference between Fs and Fs′ by checking the availability of incomingdata samples. For example, if Fs′ is faster, then it will run out ofsamples to use.

Referring now to FIG. 8 in conjunction with FIGS. 6-7, instead oftransmitting audio utilizing a digital-to-analog converted analog levelcorresponding to the digital code (e.g., as discussed in FIGS. 1-5above), downstream audio transmission waveform 800 may be utilized. Asshown in FIG. 8, waveform 800 may include video blanking interval 802having sync pulse 816, digital start code pattern 804, audio data 806,and digital end code pattern 806 contained therein. For example, in someembodiments, arbiter 608 together with video formatter 610 manage thedetection of the video blanking period interval 802 in A/V stream 616.This may be performed in a same or similar manner as video encoder 110and arbiter 108 as taught in the discussion of FIGS. 1-5 above. In someembodiments, A/V stream 616 is the final output generated by arbiter 608and video formatter 610. Arbiter 608 gets the timing informationincluding, for example, H/V sync, line count and pixel count, fordetermining the proper video blanking period that the audio data packetcan be inserted.

In some embodiments, the format of the transmitted audio datacorresponding to A/V stream 616 may correspond to a serial digital datastream in native form. For example, start code pattern 804 may beinitially sent and followed by sampled digital audio data 806 in serialbit stream format, with optional redundancy bits for error correction.In one embodiment, digital audio data 806 may be in its native formtransmitted high bit first. In another embodiment, digital audio data806 may be in its native form transmitted low bit first. In someembodiments, arbiter 608 and audio extractor 708 may process digitalaudio data 806 with or without error correction capability.

In some embodiments, A/V stream 616 may be encoded for various purposesincluding facilitating a user communication channel between upstream anddownstream users. In some embodiments, other types of data payload maybe implemented (e.g., meta data related to the video or control data. Inthese embodiments, maintaining periodicity may not be important and thesynchronizer/extrapolator in the receiver side may not be needed.

Discussed in further detail below, in some embodiments, depending on theblanking space (i.e., vertical blanking space or horizontal blankingspace), two or more digital audio data samples may be transmitted basedon the predefined protocol. For example, in the analog domain, one audiosample is represented by one variable height pulse. More audio samplesmay be sent under the same header by adding more sample pulses after thefirst sample. This is similar for the digital case. The number ofsamples to be sent together need to be predefined so receiver knows howmany samples to retrieve. In the case of variable number of samples, anend-of-transmission flag is needed after the valid sample to indicate nomore valid sample. In some embodiments, transmitting audio data in anative digital format superimposed (i.e., on top) of the analog videomay be extended to two-way simultaneous audio communication, which isdiscussed in further detail below.

Referring now to FIGS. 9-11; FIGS. 9-10 depict embodiments correspondingto a video transmission protocol that includes functionality for 2-waysimultaneous audio transmission by utilizing an upstream channel. Videoreceiver 900 and video transmitter 1000 block diagrams may be similar totransmitter/receiver 600, 700 as depicted in FIG. 6 and FIG. 7, whereinsimilarly labeled parts and numbers correspond to similar structureshaving similar functionality with respect to the ones and tens positionnumbers. Accordingly, FIG. 9 illustrates a block diagram of videoreceiver 900 that includes an opposite direction audio signaltransmitter configured for upstream (reverse) audio transmission, andFIG. 10 illustrates a block diagram of video transmitter 1000 thatincludes an opposite direction signal receiver configured for upstream(reverse) audio receiving.

Although the processing for the audio transmission and reception aresimilar to the downstream audio processing as described above in FIGS.6-8 (e.g., similar to transmitter/receiver 600,700), the method of audiodata insertion and extraction for upstream/opposite direction audiotransmitter 901 and upstream audio receiver 1001 are different due tothe fact that video transmission is one way (downstream) only. Forexample, for the TDMA operation in this case, the available space forother uses that is not occupied by the video data and videosynchronization timing are the video blanking time, either line(horizontal) blanking or field/frame (vertical) blanking. For 2-waytransmission, an exemplary implementation is to use one blanking timefor downstream and another for upstream. Otherwise, other type ofidentification will be needed like different headers so they will not bemixed up.

For example, typically, the downstream data is transmitted in thehorizontal blanking time excluding the vertical blanking lines. Theupstream data is transmitted in the predefined vertical blanking linesnot used for other purposes. Accordingly, the upstream audiotransmission protocol as described herein facilitates reverse directiontransmission (e.g., upstream transmission from video receiver 700 tovideo transmitter 600) by utilizing the vertical blanking lines ofanalog video-in signal 603, which have not been used for video ordownstream audio transmission. In general, they occupy lines that aremutually exclusive, i.e. the horizontal blanking time in those verticalblanking lines used for upstream transmission will not be used fordownstream transmission. Due to this fact and the fact that the videoline period frequency is different than the audio sample frequency, theupstream audio transmission is also not periodic. The upstream audiodata are collected over the frame period before transmitting all duringthe vertical blanking lines and transmission is also not periodic.Therefore, converting back to the periodical signal at receiver sideusing local Fs′ is required.

As shown by the dashed line in FIGS. 9-10, in some embodiments, videoreceiver 900 includes upstream/opposite direction audio transmitter 901.Video receiver 900 resides on the video receiver side (e.g.,corresponding to video receiver 700). Video transmitter 1000 includesupstream/opposite direction audio receiver 1001. Video transmitter 1000resides on the video transmitter side (e.g., video transmitter 600).Upstream audio transmitter 901 and upstream audio receiver 1001 areconfigured for implementing 2-way simultaneous audio transmission, asdiscussed in detail below.

FIG. 11 depicts an exemplary upstream audio transmission waveform 1100,in accordance with some embodiments described herein. In order toachieve the minimum audio sample rate (e.g., 8K, 16K, or 32 samples persecond), due to limited vertical/horizontal blanking lines per frame inthe video signal, multiple digital audio samples may be transmitted perhorizontal line. As depicted in FIG. 11, the transmission on each videoblanking line 1102 starts with digital start pattern 1104 followinghorizontal sync (HS). Digital start pattern 1104 may be followed bymultiple digital audio data samples 1106 _(N). In some embodiments, endpattern 1108 may be implemented to indicate the end of audio datasamples 1106 _(N). In some embodiments, end pattern 1108 may be utilizedwhen the number of audio sample varies per line. In other embodiments, afixed number of samples is predetermined per line. When a predeterminedfixed number of samples per line is implemented, an end pattern is notrequired.

In some embodiments, arbiter 908 of upstream audio transmitter 901relies on video decoder 910 to determine proper vertical blanking linesof the incoming video (corresponding to 603 in FIG. 6) and the timeslots within vertical blanking line for transmission. For example,arbiter 908 may retrieve audio data from the FIFO buffer 906 and formatthe signal with start code 1104 and one or more audio data samples 1106_(N) for proper transmission. The start code and/or end code pattern1106, 1108 for each line are inserted before being electricallysuperimposed onto the incoming video signal (corresponding to 603 inFIG. 6) by combiner 912. By such insertion, a start and/or end code1104, 1108, may be detected on the video transmitter side by upstreamaudio receiver 1001, as discussed in FIG. 10.

Referring back now to FIG. 10, in some embodiments, upstream audioreceiver 1001 on the video transmitter 1000 retrieves information fromvideo formatter 1010 for determining which video blanking line(s) tomonitor according to predefined protocol. In some embodiments, thepredefined protocol includes the start code format, bit pulse duration,number of bits per sample, samples per line in the case of fixed number,end code, signed/unsigned, bit order (MSB or LSB first). Upstream audioreceiver 1001 then extracts digital audio samples utilizing audioextractor 1008. Audio extractor 1008 may extract audio data samples 1106_(N) following detection of start code 1104. Upon detecting start code1104, audio extractor 1008 transmits audio data samples 1106 _(N) toFIFO buffer 1006. FIFO buffer 1006 stores sampled audio data inchronological order to be reconstructed by synchronizer 1012. In someembodiments, synchronizer 1012 retrieves data from FIFO buffer 1006 andcalculates audio output samples based on the receiver audio clock rateFs′, which should be substantially same as transmitter rate Fs, whichcan use interpolation, also called rate matching as discussedpreviously. Substantially same means the same frequency but they can beoff by few hundred ppm depending the accuracy of the reference clock(i.e., the difference is negligible). The clocks are also notsynchronized or having any fixed phase or frequency relationship. Forexample, the calculation here is similar to what has been describedabove for downstream receiver. The data is considered packetized insteadof periodic in time domain.

With respect to interpolation, the audio data rate matching between twosubstantially same but independent sampling clocks on the transmitter(such as PLL 605 in FIG. 6) and receiver (such as PLL 705 in FIG. 7). Toreconstruct the audio data on the audio receiver side (with the upstreamaudio receiver 1001 on the video transmitter 1000; see also FIG. 6)based on the local free running audio clock (not shown), re-sampling ofthe incoming audio data sampled with transmitter clock (such as PLL 605in FIG. 6) is required. The arbiter (such as arbiter 608 in FIG. 6)monitors the rate difference between the incoming data stored into theFIFO 1006 and the target output sampling rate that retrieves data fromthe FIFO 606. The re-sampling position of the data at the output of theFIFO 1006 is then dynamically adjusted at the synchronizer 1012 based onthis rate difference in order to correctly reconstruct the originalaudio signal using the local free running audio clock. Thisinterpolation is illustrated in the diagram shown in FIG. 12.While interpolation is described immediately above with reference to thetransmitter 600 of FIG. 6 and transmitter 1000 of FIG. 10 that includesthe audio receiver 1001, such interpolation can also be used withrespect to the audio that is received at the downstream side, such as atreceiver 700 illustrated in FIG. 7.

Although the present invention has been particularly described withreference to the preferred embodiments thereof, it should be readilyapparent to those of ordinary skill in the art that changes andmodifications in the form and details may be made without departing fromthe spirit and scope of the exemplary embodiments described herein. Itis intended that the appended claims encompass such changes andmodifications.

What is claimed:
 1. A method for transmission of audio over analog video data with a single cable to a receiver, the method comprising: receiving, at a transmitter a digital video signal and an audio signal, wherein the audio signal is one of an analog audio signal or a digital audio signal; sampling, by an audio analog-to-digital converter (ADC), the audio signal if the audio signal is the analog audio signal; storing, in a First-in-First-Out (FIFO) buffer, digital audio data corresponding to the sampled analog audio signal or the digital audio signal; reading, by an arbiter, the digital audio data, in response detecting an availability of data in the FIFO buffer; formatting serialized audio bits with a digital start code from the digital audio data; inserting the serialized audio bits with the digital start code into a blanking period of the digital video signal, thereby generating a combined digital audio and video signal; converting, by a digital-to-analog converter (DAC), the combined digital audio and video signal to analog, thereby generating a combined analog audio and video stream including audio data in a native form; and transmitting the combined analog audio and video stream over the single cable in one direction to the receiver.
 2. The method of claim 1, further comprising: receiving, by the receiver, the combined analog audio and video signal; converting, by another ADC included within the receiver, the combined analog audio and video signal to a combined digital audio and video signal, extracting an audio data stream from the combined digital audio and video signal.
 3. The method of claim 2, further comprising: storing the audio data stream into another FIFO, retrieving the audio data samples from the another FIFO at a rate that is substantially the same as the audio sample frequency at the transmitter side and reconstructing the audio samples periodically into a continuous audio stream; and outputting the continuous audio stream.
 4. The method of claim 3, wherein the step of retrieving and reconstructing interpolates the audio data samples based upon a frequency difference between the receiver and transmitter.
 5. The method of claim 1, further comprising a method of two-way audio transmission, wherein the sampled audio signal is sampled at a first frequency, wherein the transmitter includes a opposite direction audio signal receiver, and wherein the receiver includes an opposite direction audio signal transmitter, comprising: receiving, at the opposite direction audio signal transmitter included within the receiver, a second audio signal that is one of a second analog audio signal and a second digital audio signal; determining, by an arbiter of the opposite direction audio transmitter and a video decoder of the receiver, one or more vertical blanking lines of the combined analog audio and video stream and one or more time slots within the one or more vertical blanking lines without audio data; sampling, by another analog-to-digital converter (ADC) disposed within the opposite direction audio signal transmitter, the second analog audio signal at a second frequency if the second audio signal is the second analog audio signal; storing, in another First-in-First-Out (FIFO) buffer disposed within the opposite direction signal transmitter, second digitized audio samples corresponding to one of the second digital audio signal and the second sampled analog audio signal inserting a start pattern and one or more second serialized audio data and an end pattern into a vertical blanking interval of the combined analog audio and video stream; transmitting, by the opposite direction signal transmitter disposed within the receiver to the opposite direction signal receiver disposed within the transmitter, an audio stream corresponding to the start and/or end patterns and the second serialized audio bits to the transmitter that includes the audio receiver, wherein the transmitting of the audio stream occurs of the single cable in another direction opposite the one direction.
 6. The method of claim 5, further comprising: receiving, by the opposite direction signal receiver disposed within the transmitter, the audio stream; extracting the second serialized audio data based on the one or more vertical blanking lines and one or more time slots into second extracted audio samples; storing the second extracted audio samples in a further FIFO buffer disposed within the opposite direction signal receiver; and selecting an output sample frequency that is substantially the same as the sampling frequency of the opposite direction signal transmitter; and retrieving the audio samples and outputting a reconstructed audio stream based on the output sample frequency.
 7. The method of claim 6, wherein the step of retrieving and outputting interpolates the audio samples based upon a frequency difference between the receiver and transmitter. 